Determining presence of radio frequency communication device

ABSTRACT

A RF data communication device operates in at least two states. In a first state, the device transmits a response to an RF transmission if specific data therein represents an inquiry as to the presence of one or more RF data communication devices and if specific data therein corresponds to a class maintained by the device. The device does not transmit a response if specific data in the RF transmission is not representative of an inquiry as to the presence of one or more RF data communication devices, or if specific data therein does not correspond to at least one maintained class. In a second state, the device does not transmit a response when specific data is included therein that is representative of an inquiry as to the presence of one or more RF data communication devices and specific data therein corresponds to at least one maintained class.

I. CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present patent application is a U.S. continuation patent applicationof, and claims priority under 35 U.S.C. §120 to, U.S. patent applicationSer. No. 12/343,822, filed Dec. 24, 2008, which published as U.S. patentapplication publication no. US 2009/0103462, and which '822 applicationis a U.S. continuation patent application of, and claims priority under35 U.S.C. §120 to, U.S. patent application Ser. No. 11/618,931, filedJan. 1, 2007, which published as U.S. patent application publication no.US 2007/0155327, and which '931 application is a U.S. nonprovisionalpatent application of, and claims priority under 35 U.S.C. §119(e) to,U.S. patent application Ser. No. 60/766,223, filed Jan. 1, 2006. Each ofthese patent applications and publications is hereby incorporated hereinby reference.

The present application further hereby incorporates by reference each ofthe following patent application publications and patents, each of whichis owned by the assignee of the present application: U.S. Pat. Nos.7,155,264; 7,133,704; 6,934,540; 6,745,027; U.S. patent applicationpublication no. US 2006/0018274; U.S. patent application publication no.US 2005/0215280; U.S. patent application publication no. US2006/0023679; U.S. patent application publication no. US 2006/0023678;U.S. patent application publication no. US 2006/0023678; U.S. patentapplication publication no. US 2006/0023679; U.S. patent applicationpublication no. US 2006/0237490; U.S. patent application publication no.US 2006/0276963; U.S. patent application publication no. US2006/0282217; U.S. patent application publication no. US 2006/0276161;U.S. patent application publication no. US 2006/0289204; U.S. patentapplication publication no. US 2006/0274698; U.S. patent applicationpublication no. US 2006/0287822; and U.S. patent application publicationno. US 2006/0287008.

II. COPYRIGHT STATEMENT

All of the material in this patent document is subject to copyrightprotection under the copyright laws of the United States and othercountries. The copyright owner has no objection to the facsimilereproduction by anyone of the patent document or the patent disclosure,as it appears in official governmental records but, otherwise, all othercopyright rights whatsoever are reserved.

III. BACKGROUND OF THE INVENTION

Conventional systems for tracking and/or monitoring assets (hereingenerally referred to as “asset tracking systems”) utilize wireless tagsthat generally respond to any broadcast that is made. The wireless tagsusually are passive, and the responses that the passive wireless tagsmake are often referred to as “chirps.”

More sophisticated asset tracking systems utilize semi-passive wirelesstags and/or active wireless tags. A semi-passive wireless tag includesan internal power source for transmitting, and an active wireless tagincludes an internal power source for both receiving and transmitting.Semi-passive and active wireless tags generally have greatercapabilities than passive wireless tags due to the internal powersources. Of course, power consumption is always a concern when awireless tag includes an internal power source, since the internal powersupply limits the useful life of the wireless tag, after which timemaintenance is required (e.g., replacement of the internal powersource).

In improved asset tracking systems, such as those disclosed in the abovepatent applications and patents that have been incorporated herein byreference, a wireless tag responds to a broadcast if the broadcastincludes a common designation matching a common designation of thewireless tag. Such a common designation may comprise, for example, an“asset class” associated with the wireless tag. Ad hoc networks furthermay be created based on such classes, which ad hoc networks are referredto as “class based” networks.

Class based networks (and common designation networks in general) arebeneficial because, in such networks, a communication device, such as awireless tag, generally only transmits a response to a broadcast if thebroadcast includes a class (or common designation) that matches a class(or common designation) of that communication device. Indeed, in acommunication device employing a wakeup sequence of one or more of thepatent references incorporated herein by reference, such communicationdevice does not even process a broadcast once it is determined that thebroadcast fails to include a matching class of the communication device.Consequently, the internal power supply of a semi-passive or activecommunication device is not drained by needless processing and/orresponses to broadcasts.

In asset tracking systems, it often is important to know the physicallocation of an asset. This could include knowing where the asset iswithin a limited physical area, such as a warehouse; this also couldinclude knowing where the asset is within several different warehousesin several different geographical locations, as well as where the assetis during transit between such locations.

In a conventional asset tracking system in which communication devicescomprising semi-passive or active radios are placed on the assets, aconventional method for acquiring visibility of the assets includesbroadcasting within an area at regular intervals to solicit responsesfrom all of the radios within the area. The responses from the radiosreveal the radios, and thus the assets, that are in the area.

This method is not advantageous because the regular, repetitivebroadcasts result in an unnecessary power drain of the respondingradios. Interference also can occur if a large number of radios respondat the same time, thereby making it difficult to accurately identify allof the radios within the area that respond to the broadcast.

In an alternative conventional method, a timer is included with eachradio and the radio is configured to transmit at periodic intervals as afunction of the timer. The radio thereby alerts the tracking system asto the whereabouts of the radio and, thus, the asset with which it isassociated. By including timers with each radio, the radios may transmitat differing times in order to avoid unnecessary interference. A radioalso can be set to sleep between intervals and to be awoken by the timerfor making its regular transmissions. This increases the useful life ofthe radios because the radios do not consume power by actively listeningfor broadcasts while sleeping.

This alternative method permits determinations as to the delivery andcontinued presence of an asset at a particular area. Nevertheless, thisalternative method does include drawbacks. For instance, by usingtimers, the radios are inaccessible by the asset tracking system duringthe sleep periods. Another drawback is that the radios automaticallyawake and transmit without regard for their location and without regardfor whether the transmission is actually warranted or even desired. Inthis respect, during transportation on a plane, a radio may awaken andtransmit, which may cause unwanted interference with the operation ofthe airplane. Preprogrammed transmission at regular intervals also mayreveal the presence of the asset to unauthorized persons snooping forsuch radio transmissions.

Accordingly, better asset tracking systems and methods are desired thatminimize unnecessary power consumption and that reduce unnecessarytransmissions by communication devices associated with assets.

IV. SUMMARY OF THE INVENTION

The present invention includes many aspects and features. Moreover,while many aspects and features relate to, and are described in, thecontext of asset tracking systems, the present invention is not limitedto use only in asset tracking systems, as will become apparent from thefollowing summaries and detailed descriptions of aspects, features, andone or more embodiments of the present invention. For instance, one ormore aspects of the present invention may be utilized to determine thepresence or arrival of a communication device within an area independentof any asset and/or independent of any asset tracking system. Thepresent invention also is not limited to use in common designation orclass-based networks, although in preferred embodiments commondesignation or class-based networks are used. Indeed, the presentapplication may beneficially be used in asset tracking as well as sensormonitoring, hazmat monitoring, first responder scenarios, militaryactivities and situations, mobile phone applications, and automobiledealer key tracking systems.

Accordingly, an aspect of the present invention relates to a radiofrequency communication device that includes a receiver configured toreceive radio frequency transmissions; a transmitter configured to makeradio frequency transmissions; an interface for receiving a signal froma sensor (hereinafter “sensor signal”); and electronic components. Inaccordance with this aspect of the invention, the electronic componentsare arranged and configured such that the radio frequency communicationdevice operates in at least two states.

In the first state, the radio frequency communication device responds toa radio frequency transmission that is received by the receiver and thatincludes data representative of an inquiry as to the presence of radiofrequency communication devices within an area. The “data representativeof an inquiry as to the presence of radio frequency communicationdevices within an area” simply may be a predefined value in a particularformat within the broadcast in accordance with a predefined protocol. Aradio frequency transmission that includes such data is sometimesreferred to herein as a “Present Broadcast.” The response to the PresentBroadcast is made by the radio frequency communication device by makinga radio frequency transmission with the transmitter that includes anidentification of the radio frequency communication device. A radiofrequency transmission that includes an identification of the radiofrequency communication device making the transmission, and that is madein response to a Present Broadcast, is sometimes referred to herein as a“Present Response.”

In the second state, the radio frequency communication device does notrespond to a Present Broadcast with a Present Response; specifically, noresponse to a Present Broadcast comprising a radio frequencytransmission is made with the transmitter that includes anidentification of the radio frequency communication device, andpreferably, no response to a Present Broadcast comprising a radiofrequency transmission is made at all, whether including anidentification of the radio frequency communication device or otherwise.

In further accordance with this aspect of the invention, the electroniccomponents are arranged and configured such that the radio frequencycommunication device enters the second state from the first state uponresponding to a Present Broadcast with a Present Response. Theelectronic components further are arranged and configured such that theradio frequency communication device enters the first state from thesecond state upon receiving, through the interface, a sensor signalbased on sensor-acquired data that is indicative of a predeterminedcondition. The sensor signal itself may include the sensor-acquired dataor may be representative of the sensor-acquired data and may indicate,for example, a state of the sensor. In any event, such sensor signal isdeemed to provide “sensor-acquired information” through the interface.

In a feature of this aspect, the first and second states relate only towhether the communication device responds to a Present Broadcast. Thus,the communication device otherwise remains responsive to otherbroadcasts in general and/or remains responsive to transmissionsdirected to the device. For example, in class-based networks, thecommunication device preferably remains responsive to any transmissionincluding a class to which it is a member, whether the communicationdevice is in the first state or the second state. Such transmission tothe communication device may relate to a change in sensor states;maintenance of the communication device (e.g., checking the status ofthe internal power supply); or enabling or disabling of certain featuresor capabilities of the communication device (including the practicing ofthe present invention). In an alternative—and less preferred—feature,the first and second states relate not only to whether the communicationdevice responds to a Present Broadcast, but whether the communicationdevice responds to any broadcast at all. In this respect, when thecommunication device is in the second state, the communication devicemay not respond to any broadcasts at all.

In yet another feature of this aspect, the electronic components arefurther configured such that the radio frequency communication devicemakes a radio frequency transmission upon receiving, through theinterface, sensor-acquired information that indicates a predeterminedcondition.

In another feature of this aspect, the radio frequency communicationdevice further includes a computer processor that processes receivedradio frequency transmissions and received sensor-acquired information.The computer processor preferably effects state changes of the radiofrequency communication device as a function of received radio frequencytransmissions and received sensor-acquired information.

In still yet another feature, the communication device enters the firststate from the second state after a predetermined period of time hastranspired according to a timer of the communication device. Thisfeature is beneficial, for example, if a sensor associated with an radiofrequency communication device fails and if the radio frequencycommunication device would not otherwise enter the first state from thesecond state. In this regard, the time period before the radio frequencycommunication device enters, by default, the first state from the secondstate may be a significant period of time.

In still yet another feature, the communication device enters the firststate from the second state after a predetermined number of failedattempts to communicate with a server have occurred. This feature isbeneficial, for example, in identifying radio frequency communicationdevices in a certain area that are having technical difficulties intheir communications.

In still another feature, the radio frequency communication deviceenters the first state from the second state upon receipt, via thereceiver of radio frequency communication device, of an instruction toenter the first state. The instruction may be specific to a particularradio frequency communication device or generic to a plurality of radiofrequency communication devices. Furthermore, a special commondesignation, such as a special class, may be utilized whereby abroadcast to such common designation would instruct radio frequencycommunication device having that common designation to enter the firststate. This feature is beneficial, for example, if a sensor associatedwith an radio frequency communication device fails and if the radiofrequency communication device would not otherwise enter the first statefrom the second state. This enables, for example, a sever to look for aradio frequency communication device within a particular area.

Another aspect of the invention relates to a method performed by a radiofrequency communication device. The method includes: the first steps ofresponding to a Present Broadcast with a Present Response and then notresponding to any further Present Broadcasts; and, repeating the firststeps upon receiving, through an interface of the radio frequencycommunication device, sensor-acquired information that is indicative ofa predetermined condition. Thus, after receiving such sensor-acquiredinformation, the radio frequency communication device does, in fact,respond to the next Present Broadcast.

In a feature of this aspect of the invention, the method furtherincludes the step of making a radio frequency transmission with thetransmitter of the radio frequency communication device upon receiving,through an interface of the radio frequency communication device, thesensor-acquired information indicative of the predetermined condition.

In accordance with this and other aspects of the invention, thepredetermined condition may comprise movement of the radio frequencycommunication device; a change, exceeding a threshold, with respect tothe location of the radio frequency communication device as determinedbased on GPS data; an/or a temperature associated with the radiofrequency communication device exceeding a predetermined threshold. Withfurther respect to location, for example, the data from the GPS receivermay be compared against a range of x-y coordinates for “geo fencing” ofthe communication device (e.g., 89.2412<x,89.4522 and145.2332<y<145.8772), with a predetermined condition being triggered bythe GPS data that indicates the communication device being outside of apredefined geographical area. An examples of this is described belowwith regard to FIGS. 1-8.

In further accordance with the invention, the predetermine condition maycomprise a change in state of a sensor associated with a radio frequencycommunication device and the sensor may or may not indicate movementfrom an area. Such a state change could indicate, for example, thebreaking of a magnetic seal or other seal of a container wherein thesensor monitors the seal of the container. The container could be, forexample, a hazardous waste container or an international shippingcontainer. In such case, the Present Broadcast could be used to revealthose containers for which the seals have been broken.

In another feature of the invention, the radio frequency communicationdevice may comprises a node in one or more common designation networks.In this respect, the data representative of a general inquiry as to thepresence of radio frequency communication devices may be a predefinedcommon designation. Indeed, the data representative of a general inquiryas to the presence of radio frequency communication devices may be acommon designation of “present.”

In a related feature, the radio frequency communication device isassociated with an asset being tracked in an asset tracking system. Theasset tracking system may be a class based asset tracking system, andthe data representative of a general inquiry as to the presence of radiofrequency communication devices may be a predefined class designation.Indeed, the data representative of a general inquiry as to the presenceof radio frequency communication devices may be a class designation of“present.”

In addition to the aforementioned aspects and features of the presentinvention, the present invention further includes the various possiblecombinations of such aspects and features.

It will be appreciated that, in accordance with one or more aspects,determinations can be made as to when an asset has arrived in an areaand when an asset has left the area. Furthermore, this can be achievedwithout significantly reducing battery life, and this can be achievedwithout unnecessary radio frequency transmissions.

V. BRIEF DESCRIPTION OF THE DRAWINGS

One or more preferred embodiments of the present invention now will bedescribed in detail with reference to the accompanying drawings,wherein:

FIG. 1 is a first illustration representative of locations, states, andstate transitions of radio frequency communication devices, at a firsttime, in accordance with one or more preferred embodiments of thepresent invention.

FIG. 2 is a second illustration representative of locations, states, andstate transitions of radio frequency communication devices, at a secondtime subsequent to the first time, in accordance with one or morepreferred embodiments of the present invention.

FIG. 3 is a third illustration representative of locations, states, andstate transitions of radio frequency communication devices, at a thirdtime subsequent to the second time, in accordance with one or morepreferred embodiments of the present invention.

FIG. 4 is a fourth illustration representative of locations, states, andstate transitions of radio frequency communication devices, at a fourthtime subsequent to the third time, in accordance with one or morepreferred embodiments of the present invention.

FIG. 5 is a fifth illustration representative of locations, states, andstate transitions of radio frequency communication devices, at a fifthtime subsequent to the fourth time, in accordance with one or morepreferred embodiments of the present invention.

FIG. 6 is a sixth illustration representative of locations, states, andstate transitions of radio frequency communication devices, at a sixthtime subsequent to the fifth time, in accordance with one or morepreferred embodiments of the present invention.

FIG. 7 is a seventh illustration representative of locations, states,and state transitions of radio frequency communication devices, at aseventh time subsequent to the sixth time, in accordance with one ormore preferred embodiments of the present invention.

FIG. 8 is an eighth illustration representative of locations, states,and state transitions of radio frequency communication devices, at aneighth time subsequent to the seventh time, in accordance with one ormore preferred embodiments of the present invention.

VI. DETAILED DESCRIPTION

As a preliminary matter, it will readily be understood by one havingordinary skill in the relevant art (“Ordinary Artisan”) that the presentinvention has broad utility and application. Furthermore, any embodimentdiscussed and identified as being “preferred” is considered to be partof a best mode contemplated for carrying out the present invention.Other embodiments also may be discussed for additional illustrativepurposes in providing a full and enabling disclosure of the presentinvention. Moreover, many embodiments, such as adaptations, variations,modifications, and equivalent arrangements, will be implicitly disclosedby the embodiments described herein and fall within the scope of thepresent invention.

Accordingly, while the present invention is described herein in detailin relation to one or more embodiments, it is to be understood that thisdisclosure is illustrative and exemplary of the present invention, andis made merely for the purposes of providing a full and enablingdisclosure of the present invention. The detailed disclosure herein ofone or more embodiments is not intended, nor is to be construed, tolimit the scope of patent protection afforded the present invention,which scope is to be defined by the claims and the equivalents thereof.It is not intended that the scope of patent protection afforded thepresent invention be defined by reading into any claim a limitationfound herein that does not explicitly appear in the claim itself.

Thus, for example, any sequence(s) and/or temporal order of steps ofvarious processes or methods that are described herein are illustrativeand not restrictive. Accordingly, it should be understood that, althoughsteps of various processes or methods may be shown and described asbeing in a sequence or temporal order, the steps of any such processesor methods are not limited to being carried out in any particularsequence or order, absent an indication otherwise. Indeed, the steps insuch processes or methods generally may be carried out in variousdifferent sequences and orders while still falling within the scope ofthe present invention. Accordingly, it is intended that the scope ofpatent protection afforded the present invention is to be defined by theappended claims rather than the description set forth herein.

Additionally, it is important to note that each term used herein refersto that which the Ordinary Artisan would understand such term to meanbased on the contextual use of such term herein. To the extent that themeaning of a term used herein—as understood by the Ordinary Artisanbased on the contextual use of such term—differs in any way from anyparticular dictionary definition of such term, it is intended that themeaning of the term as understood by the Ordinary Artisan shouldprevail.

Furthermore, it is important to note that, as used herein, “a” and “an”each generally denotes “at least one,” but does not exclude a pluralityunless the contextual use dictates otherwise. Thus, reference to “apicnic basket having an apple” describes “a picnic basket having atleast one apple” as well as “a picnic basket having apples.” Incontrast, reference to “a picnic basket having a single apple” describes“a picnic basket having only one apple.”

When used herein to join a list of items, “or” denotes “at least one ofthe items,” but does not exclude a plurality of items of the list. Thus,reference to “a picnic basket having cheese or crackers” describes “apicnic basket having cheese without crackers”, “a picnic basket havingcrackers without cheese”, and “a picnic basket having both cheese andcrackers.” Finally, when used herein to join a list of items, “and”denotes “all of the items of the list.” Thus, reference to “a picnicbasket having cheese and crackers” describes “a picnic basket havingcheese, wherein the picnic basket further has crackers,” as well asdescribes “a picnic basket having crackers, wherein the picnic basketfurther has cheese.”

Turning now to the drawings, FIG. 1 is representative of locations,states, and state transitions of radio frequency communication devicesshown at a first time in accordance with one or more preferredembodiments of the present invention.

In this regard, nine radio frequency communication devices 10 labeled“RSI R₁” through “RSI R₉” are shown in FIG. 1. Each radio frequencycommunication device 10 preferably comprises a movable remote sensorinterface or “RSI” that includes its own internal power source, such asa battery. Each RSI preferably is active or at least semi-active, andeach RSI preferably is disposed in electronic communication with one ormore sensors through one or more interfaces of the RSI for receivingsensor signals including, for example, sensor-acquired data. Suchsensors may comprise, for example, temperature sensors, motion sensors,accelerometer sensors, and GPS receivers.

The nine communication devices 10 are distributed among m differentphysical areas (m being some integer greater than 1). These areas arerepresented by areas 12,14,16,18 illustrated in FIG. 1. Each area may beat the same location as another area or at a different location asanother area. For instance, area 12 may represent a boat dock (area) ata port of entry (location) and area 14 may represent a truck loadingdock (area) at the same port of entry (location). Alternatively, area 12may represent a warehouse (area) in Charleston, S.C. (location) and area14 may represent a warehouse (area) in San Diego, Calif. (location).Moreover, area 16 may represent the cargo area (area) of a transportvehicle (location) in route between area 12 in Charleston and area 14 inSan Diego, and the location thus need not be stationary. In thisexample, the location is dynamic and changes as the transport vehiclemoves between Charleston and San Diego.

Furthermore, in accordance with one or more aspects of the presentinvention, at least one of the sensors associated with an RSI isutilized to indicate the likely removal of the RSI from an area, asdiscussed in greater detail below.

Each of the m areas includes at least one gateway and, accordingly,there are at least m gateways represented in FIG. 1. These gateways arerepresented by gateways 20,22,24,26. In this regard, gateway 20 isillustrated as being within area 12 and is labeled “Gateway G₁”; gateway22 is illustrated as being within area 14 and is labeled “Gateway G₂”;gateway 24 is illustrated as being within area 16 and is labeled“Gateway G₃”; and gateway 26 is illustrated as being within area 18 andis labeled “Gateway G_(m)”.

Each gateway 20,22,24,26 preferably is disposed in electroniccommunication with one or more servers labeled, respectively, “ServerS₁”, “Server S₂”, and “Server S_(n)”, wherein n is some integer greaterthan 1. The servers are represented by server 28,30,32 and may beremotely located to each other. The servers 28,30,32 also may beremotely located to the gateways 20,22,24,26. The electroniccommunication between the servers and the gateways may be accomplished,for example, by way of cellular communications, satellitecommunications, and/or Internet communications.

Preferably, the communication devices 10 are associated with assets, andthe servers 28,30,32 collectively include the programs and databases ofone or more asset tracking systems for tracking and/or monitoring of theassets with which the communication devices 10 are associated. Thegateways and the communication devices further preferably form commondesignation networks and, more preferably, class based networks.

With further reference to FIG. 1, each gateway 20,22,24,26 is shown at afirst time t₁ in FIG. 1 as making a respective radio frequencytransmission that preferably awakens each communication device 10 from asleep or standby mode, as appropriate. In this regard, this radiofrequency transmission preferably comprises a wakeup broadcast thatincludes a common designation comprising a class designation. If theclass designation matches a class designation maintained in a table ofclass designations of a respective communication device 10, then thatcommunication device 10 awakens and makes a radio frequency transmissionin response. For brevity, a radio frequency transmission that is awakeup broadcast and that includes a class designation is sometimesreferred to herein as a “Class-Present Wakeup Broadcast” and is simplylabeled “Present” in the drawings. As will be appreciated, theClass-Present Wakeup Broadcasts represent a particular type of—and if asubset of—Present Broadcasts.

Additionally, the transmission in response to the Class-Present WakeupBroadcast by the respective communication device 10 preferably includesan identification of the respective communication device 10. Such anidentification may uniquely identify the respective communication device10 or radio of the communication device 10. Alternatively, theidentification may uniquely identify one or more assets with which thecommunication device 10 is associated in an asset tracking system,especially when the communication device is a wireless reader tag (WRT)or similar device. Alternatively, the identification may serve todistinguish the respective communication device 10 from one or moreother communication devices 10 without uniquely identifying therespective communication device 10 from all other communication devices10.

The Class-Present Wakeup Broadcast made by each gateway 20,22,24,26 isreceived by each communication device within the respective area of thegateway, and each communication device 10 is shown as responding to theClass-Present Wakeup Broadcast, wherein each response is represented bya lightning bolt.

As will be appreciated, an RSI further can retransmit the Class-PresentWakeup Broadcast to other RSIs that fall outside of the gateway range,thereby expanding the effective range of communications with thegateway. Communications between a gateway and one or more RSIs outsideof the gateway's range, via one or more RSIs within range, is disclosedin one or more of the incorporated references but, for clarity, is notshown in the present drawings. Communications between an RSI and agateway further may be through other RSIs even when all RSIs are withinrange of the gateway, as disclosed, for example, in many of theincorporated references such as U.S. Pat. Nos. 6,745,027 and 6,934,540.

As will be appreciated from the following detailed description, and inaccordance with preferred embodiments of the invention, the fact thateach of the nine communication devices 10 responds to the Class-PresentWakeup Broadcast indicates that none of the nine communication devices10 likely were present in the areas 12,14,16,18 as shown in FIG. 1 atthe time of a Class-Present Wakeup Broadcast first preceding that attime t₁. Furthermore, each communication device 10 responds to aClass-Present Wakeup Broadcast, as appropriate, regardless of the numberof times that the communication device 10 has previously responded.Whether a communication device 10 responds preferably is not a functionof the number of times that communication device 10 has responded in thepast.

The Class-Present Wakeup Broadcast may be performed by each respectivegateway “on demand” upon receipt of an instruction to such effect fromone of the servers 28,30,32. Alternatively, each gateway may beconfigured to make the Class-Present Wakeup Broadcast in accordance witha predetermined schedule, such as at regular intervals of time. Iftimers are utilized, then the timers of the gateways determine theresolution within which a communication device is identified as havingarrived at a particular area. Still yet, a particular gateway may betriggered to make a Class-Present Wakeup Broadcast by one or moresensors, such as motion, optical, or infrared sensors. Indeed, whilegateways are concurrently shown in the drawings as making Class-PresentWakeup Broadcasts, a gateway nevertheless may make a Class-PresentWakeup Broadcast independent of one or more other gateways.

The transmissions made in response to the Class-Present Wakeup Broadcastand, in particular, the identification included in each response, iscommunicated through each gateway to an appropriate one or more of theservers 28,30,32 that is tasked with keeping track of the location ofeach communication device 10. Based upon the particular gateway fromwhich a respective identification is received, the server may thendetermine that the respective communication device 10 corresponding tothat identification is within the area of that particular gateway.

Accordingly, from the responses to the Class-Present Wakeup Broadcastsshown in FIG. 1, the appropriate server determines that: RSIs R₁, R₂,and R₃ are within the area of Gateway G₁; RSIs R₄ and R₅ are within thearea of Gateway G₂; RSIs R₆, R₇, and R₈ are within the area of GatewayG₃; and RSI R₉ is within the area of Gateway G_(m). Preferably, theserver records and maintains such location information for each of thecommunication devices 10.

Thereafter, each gateway 20,22,24,26 is shown at a second timesubsequent to the first time in FIG. 2 as making a respective subsequentClass-Present Wakeup Broadcast. Again, the Class-Present WakeupBroadcast made by each gateway 20,22,24,26 is received by eachcommunication device within the respective area of the gateway; however,none of the communication devices 10 is shown as responding to theClass-Present Wakeup Broadcast. In accordance with preferred embodimentsof the invention, none of the communication devices 10 respond to theClass-Present Wakeup Broadcast because each has already responded to aClass-Present Wakeup Broadcast at time t₁, and each has yet to move fromthe respective area in which it was located since that time.

As will be appreciated, the server tasked with keeping track of thelocation of each communication device 10 receives no identification fromany communication device 10 via the gateways 20,22,24,26 and, basedthereon, does not update any location information for any of thecommunication devices 10. Having received no identifications in responseto the Class-Present Wakeup Broadcasts, the server assumes that none ofthe communication devices 10 have been moved from their respective areasas recorded by the server.

At a third time subsequent to the second time, as shown in FIG. 3,communication device 10 labeled as RSI R₂ is moved from the area 12 ofthe gateway 20 (Gateway G₁). The RSI R₂ preferably is disposed inelectrical communication with a motion sensor through an interfacethereof and, upon being moved, the RSI R₂ preferably receivessensor-acquired information from the motion sensor that indicates themovement of the RSI R₂. Such electrical communication may be wired orwireless, and the sensor may be internal or external to a housing of thecommunication device. The RSI R₂ preferably is configured, upon receiptof such sensor-acquired information through the interface, to make aradio frequency transmission including an identification thereof to anappropriate server via the gateway 20. The server preferably is theserver that records and maintains the location information for each ofthe communication devices 10 and, upon receipt of the communication fromRSI R₂, the server preferably records information pertaining to suchcommunication. In particular, the server preferably records informationindicating movement of RSI R₂ and the time t₃ of such movement. Themovement is presumed to indicate the likely removal of the RSI R₂ fromthe area. Other sensors, or a combination of sensors, further can beused to indicate such likely removal. For example, the combined readingsfrom both a motion sensor and a temperature sensor could be used toindicate likely removal of the communication device from a particulararea. Alternatively, temperature rather than motion could be used as anindicator that the communication device likely has moved from acontrolled environment of a particular area.

At a fourth time subsequent to the third time, as shown in FIG. 4,communication device 10 labeled as RSI R₄ is moved from the area 14 ofthe gateway 22 (Gateway G₂). The RSI R₄ preferably is disposed inelectrical communication with a motion sensor through an interfacethereof and, upon being moved, the RSI R₄ preferably receivessensor-acquired information from the motion sensor that indicates themovement of the RSI R₄. Such electrical communication may be wired orwireless, and the sensor may be internal or external to the RSI. The RSIR₄ preferably is configured, upon receipt of such sensor-acquiredinformation through the interface, to make a radio frequencytransmission including an identification thereof to an appropriateserver via the gateway 22. The server preferably is the server thatrecords and maintains the location information for each of thecommunication devices 10 and, upon receipt of the communication from RSIR₄, the server preferably records information pertaining to suchcommunication. In particular, the server preferably records informationindicating movement of RSI R₂ and the time t₄ of such movement.

At a fifth time subsequent to the fourth time, as shown in FIG. 5, thegateways 20,22,24,26 again make Class-Present Wakeup Broadcasts. As willbe appreciated, none of the communication devices 10 respond to theClass-Present Wakeup Broadcast that have not moved since the first timet₁; such communications generally would be unnecessary and would thusneedlessly drain power sources of the communication devices 10. On theother hand, RSI R₂ which was moved at time t₃ has since moved into thearea of gateway 24 (Gateway G₃) by time t₅ and, in response to theClass-Present Wakeup Broadcast received from gateway 24, the RSI R₂ doesmake a responsive transmission that includes an identification thereof.As a result of this responsive transmission, the server tracking thelocation information of RSI R₂ updates the location information toindicate that RSI R₂ now is in area 16 as of time t₅. RSI R₄, on theother hand, did not respond to the Class-Present Wakeup Broadcasts and,as such, its absence from areas 12,14,16,18 is identified. It furtherdeemed that it was moved from area 14 at time t₄.

At a sixth time subsequent to the fifth time, as shown in FIG. 6,communication device 10 labeled as RSI R₉ is moved from the area 18 ofthe gateway 26 (Gateway G_(m)). The RSI R₉ preferably is disposed inelectrical communication with a motion sensor through an interfacethereof and, upon being moved, the RSI R₉ preferably receivessensor-acquired information from the motion sensor that indicates themovement of the RSI R₉. Such electrical communication may be wired orwireless, and the sensor may be internal or external to the RSI. The RSIR₉ preferably is configured, upon receipt of such sensor-acquiredinformation through the interface, to make a radio frequencytransmission including an identification thereof to an appropriateserver via the gateway 26. The server preferably is the server thatrecords and maintains the location information for each of thecommunication devices 10 and, upon receipt of the communication from RSIR₉, the server preferably records information pertaining to suchcommunication. In particular, the server preferably records informationindicating movement of RSI R₉ and the time t₆ of such movement.

At a seventh time subsequent to the sixth time, as shown in FIG. 7, thegateways 20,22,24,26 again make Class-Present Wakeup Broadcasts. As willbe appreciated, none of the communication devices 10 respond to theClass-Present Wakeup Broadcast that have not moved since the precedingClass-Present Wakeup Broadcast at time t₅; such communications generallywould be unnecessary and would thus needlessly drain power sources ofthe communication devices 10. On the other hand, RSI R₉ which was movedat time t₆ has since moved into the area 14 of gateway 22 (Gateway G₂)by time t₇ and, in response to the Class-Present Wakeup Broadcastreceived from gateway 22, the RSI R₉ does make a responsive transmissionthat includes an identification thereof. As a result of this responsivetransmission, the server tracking the location information of RSI R₉updates the location information to indicate that RSI R₉ now is in area14 as of time t₇.

Additionally, RSI R₄ which was moved at time t₄ has moved into the area1 of gateway 20 (Gateway G₁) by time t₇ and, in response to theClass-Present Wakeup Broadcast received from gateway 20, the RSI R₄ doesmake a responsive transmission that includes an identification thereof.As a result of this responsive transmission, the server tracking thelocation information of RSI R₄ updates the location information toindicate that RSI R₄ now is in area 10 as of time t₇.

Thereafter, each gateway 20,22,24,26 is shown in FIG. 8 making arespective subsequent Class-Present Wakeup Broadcast at an eighth timesubsequent to the seventh. Again, the Class-Present Wakeup Broadcastmade by each gateway 20,22,24,26 is received by each communicationdevice within the respective area of the gateway; however, none of thecommunication devices 10 is shown as responding to the Class-PresentWakeup Broadcast. In accordance with preferred embodiments of theinvention, none of the communication devices 10 responds to theClass-Present Wakeup Broadcast because each communication device 10 hasalready responded as late as time t₇ to a previous Class-Present WakeupBroadcast and has yet to be moved since such time of response.Accordingly, no responsive transmissions are needlessly made by any ofthe communication devices 10.

Each of the communication devices 10 shown in FIGS. 1-8 preferablyoperates in at least two states. In a first state, a communicationdevice 10 responds to receipt of a Class-Present Wakeup Broadcast from agateway 20,22,24,26 by making a transmission that includes anidentification thereof. After this responsive transmission, thecommunication device 10 preferably enters a second state in which itdoes not respond to Class-Present Wakeup Broadcasts. The communicationdevice 10 preferably remains in this second state until sensor-acquiredinformation received through an interface thereof indicates that apredefined condition has occurred, such as movement of the communicationdevice 10. Upon the occurrence of the predefined condition, thecommunication device 10 preferably makes a transmission that includes anindication of the occurrence of the predefined condition as well as anidentification of the communication device 10. Upon making thetransmission, the communication device 10 preferably enters the firststate.

During each of the two states, the communication device 10 still wakesup and/or responds to any transmission that includes a commondesignation (such as a class designation) that matches a commondesignation of the communication device 10. Preferably, eachcommunication device 10 keeps a table of applicable common designationsto which it belongs. In this respect, a common designation preferably isused to represent the Class-Present Wakeup Broadcast and this commondesignation is either enabled or disabled in the table as maintained bythe communication device 10 depending upon whether the communicationdevice 10 should respond to a Class-Present Wakeup Broadcast that isnext received.

Specifically, after the communication device 10 has made a responsivetransmission to a Class-Present Wakeup Broadcast, the communicationdevice 10 preferably enables a motion sensor, disables the “present”common designation in its table, and waits to be awoken upon anindication of movement from the motion sensor. Furthermore, theenablement of the motion sensor and the disablement of the “present”common designation in its table may be automatically performed by thecommunication device itself following its response to the Class-BasedWakeup Broadcast, or may be performed by the communication device indirect response to instructions received from a server following theidentification of the presence of the RSI to the server.

Thereafter, once the communication device 10 moves, the communicationdevice 10 is awoken by the motion sensor and communicates, via arespective gateway, an indication of such movement to the appropriateserver. The communication device 10 also then disable the motion sensorand enables the “present” common designation for waking up of thecommunication device 10 for response to the next Class-Present WakeupBroadcast.

This algorithm for entering the two different states enables thecommunication device 10: to “check in” when it arrives within an area ofa gateway; to remain off or in standby after it has “checked in” inorder to conserve internal power and avoid spurious transmissions; andto alert an appropriate server if the communication device 10 is moved.

A benefit of at least one embodiment of the invention is the avoidanceof unnecessary and/or undesired radio frequency transmissions during airshipments in a cargo area of an airplane. Specifically, whencommunication devices 10, preferably associated with assets beingtracked and/or monitored, are loaded into the cargo area of an airplane,a Class-Present Wakeup Broadcast is made in order to identify thecommunication devices present for taking inventory of the cargo. Aninstruction then is broadcast causing the communication devices to enterthe second state, in which the motion sensors then are disabled. AClass-Present Wakeup Broadcast is not made until after the airplane hasarrived at its intended location.

Since the motion sensor is turned off when the “present” commondesignation is enabled, the communication device 10 will notcontinuously try to report back to the server while it is in motion inthe airplane. During movement, such as that associated with airtransportation, the communication device 10 thus remains in a powerconservation mode until it comes within range of the next gateway andreceives a Class-Present Wakeup Broadcast.

As will be appreciated from the foregoing description, the movement of acommunication device 10 is tightly monitored by one or more servers,since any communication device 10 within range of a gateway 20,22,24,26reports when a predefined condition, e.g., movement, has occurred thatindicates that it has been likely moved out of the respective area inwhich it was residing. Moreover, unnecessary transmissions in responseto Class-Present Wakeup Broadcasts are avoided when a communicationdevice 10 has not moved out of the respective area in which it resides.

In alternatives to the arrangements represented in FIGS. 1-8, the nservers can be consolidated into a single server; and/or one or moreservers can be combined with one or more gateways. Such changes mayreduce networking costs, delays, and overhead associated with assettracking systems, but the flexibility, capabilities, and/or robustnessof the systems likewise may be reduced.

One or more aspects of the invention further may be utilized with asingle area for maintaining visibility of assets within the single areawithout regard to visibility of the assets in other areas, if desired.

Another benefit of at least one embodiment of the invention is theability to synchronize reporting from a plurality of radio frequencycommunication devices to a server. In this respect, radio frequencycommunication devices preferably communicate data that otherwise isbeing stored to a server concurrently when responding to a PresentBroadcast. The concurrent communication of the data with a PresentResponse obviates the need for the communications device to wakeup at alater time for the specific purposes of communicating the stored data.As such, a group of communication devices can be manipulated, forexample, into the first state such that each responds to a PresentBroadcast by communicating not only a Present Response, but the storeddata at each respective communication device. Such manipulation into thefirst state can occur, for example, by creating a predeterminedcondition (e.g., change in temperature, change in location, ormovement), resulting in sensor signals causing the communication devicesto enter the first state from the second state; and/or by broadcastingan instruction to the communication devices to enter the first state.

In view of the foregoing, one or more benefits of one or more aspects ofthe present invention include: an increased battery life; the ability totransport assets by land, sea, or air without unnecessary or unwantedtransmissions from the radios associated with the assets; the ability tostill communicate “on demand” with a particular asset based on a commondesignation or class; the ability to determine assets newly arrivedwithin an area “on demand” independent of any broadcasts at regular timeintervals; the ability of an asset to “hide” from unauthorized personsby not needlessly identifying its presence in response to a generalradio frequency broadcast; and the ability to determine when an asset ismoved from an area once the asset has been identified as having arrivedwithin the area.

1. A wireless two-way radio frequency (RF) data communication devicecomprising a data packet radio component that selectively reveals itspresence in response to RF transmissions, the wireless two-way RF datacommunication device being configured to operate in a first state inwhich the wireless two-way RF data communication device: (i) receives RFtransmissions; (ii) maintains at least one common designation forpurposes of filtering RF transmissions received by the wireless two-wayRF data communication device; (iii) identifies specific data in areceived RF transmission; and (iv) in response to the received RFtransmission in which the specific data is identified, (A) transmits aresponse, (I) if the identified specific data includes datarepresentative of an inquiry as to the presence of one or more wirelesstwo-way RF data communication devices, and (II) if the identifiedspecific data includes data that corresponds to at least one maintainedcommon designation, and (B) retransmits at least a portion of thereceived RF transmission as an inquiry as to the presence of one or morewireless two-way RF data communication devices, (I) if the identifiedspecific data includes data representative of an inquiry as to thepresence of one or more wireless two-way RF data communication devices,and (II) if the identified specific data corresponds to at least onemaintained common designation whereby the wireless two-way RF datacommunication device can retransmit inquiries as to the presence of oneor more wireless two-way RF data communication devices to other wirelesstwo-way RF data communication devices.
 2. The wireless two-way RF datacommunication device of claim 1, wherein the wireless two-way RF datacommunication device enters a second state from the first state upontransmitting a response when, (a) the identified specific data includesdata representative of an inquiry as to the presence of one or morewireless two-way RF data communication devices, and (b) the identifiedspecific data includes data that corresponds to at least one maintainedcommon designation.
 3. The wireless two-way RF data communication deviceof claim 1, wherein the wireless two-way RF data communication deviceenters the first state from a second state upon receiving, through asensor interface of the wireless two-way RF data communication device,one or more sensor signals indicative of a predetermined condition. 4.The wireless two-way RF data communication device of claim 1, whereinthe wireless two-way RF data communication device enters the first statefrom a second state upon receiving a RF transmission including aninstruction to enter the first state.
 5. The wireless two-way RF datacommunication device of claim 1, wherein the wireless two-way RF datacommunication device enters the first state from a second state uponexpiration of predetermined period of time as indicated by a timer ofthe wireless two-way RF data communication device.
 6. The wirelesstwo-way RF data communication device of claim 1, wherein the wirelesstwo-way RF data communication device enters the first state from asecond state after a predetermined number of failed attempts tocommunicate by the wireless two-way RF data communication device haveoccurred.
 7. The wireless two-way RF data communication device of claim1, wherein the wireless two-way RF data communication device enters asecond state from the first state upon receiving a RF transmissionincluding an instruction to enter the second state.
 8. The wirelesstwo-way RF data communication device of claim 1, wherein the identifiedspecific data is found to correspond to at least one maintained commondesignation when the identified specific data matches at least onemaintained common designation.
 9. The wireless two-way RF datacommunication device of claim 1, wherein the at least one maintainedcommon designation comprises at least one maintained class designation,and wherein the identified specific data is found to correspond to atleast one maintained common designation when the identified specificdata matches a maintained class designation.
 10. The wireless two-way RFdata communication device of claim 1, wherein the at least onemaintained common designation comprises at least one maintained classdesignation, and wherein the identified specific data is found tocorrespond to at least one maintained common designation when theidentified specific data matches an abstracted class of the maintainedclass designation.
 11. The wireless two-way RF data communication deviceof claim 1, wherein the at least one maintained common designationcomprises at least one maintained class designation, and wherein theidentified specific data is found to correspond to at least onemaintained common designation when the identified specific data matchesa subclass of the maintained class designation.
 12. The wireless two-wayRF data communication device of claim 1, wherein the wireless two-way RFdata communication device maintains a unique identification of thewireless two-way RF data communication device in addition to the atleast one common designation used for purposes of filtering RFtransmissions received by the wireless two-way RF data communicationdevice.
 13. A data communications network, comprising: (a) a pluralityof wireless two-way radio frequency (RE) data communication devices,each wireless two-way RF data communication device forming a node of thedata communications network and each wireless two-way RF datacommunication device including a memory having stored therein at leastone common designation for purposes of filtering RF transmissionsreceived by the wireless two-way RF data communication device; (b)wherein each wireless two-way RF data communication device is configuredto operate in at least a first state, in which the wireless two-way RFdata communication device, (A) receives RF transmissions; (B) identifiesspecific data in a received RF transmission; and (C) in response to thereceived RE transmission in which the specific data is identified, (I)transmits a response, (1) if the identified specific data includes datarepresentative of an inquiry as to the presence of one or more wirelesstwo-way RF data communication devices, and (2) if the identifiedspecific data includes data that corresponds to at least one maintainedcommon designation, and (II) does not transmit a response, (1) if theidentified specific data does not include data representative of aninquiry as to the presence of one or more wireless two-way RF datacommunication devices, or (2) if the identified specific data does notcorrespond to at least one maintained common designation; and (c)wherein each wireless two-way RF data communication device is configuredto retransmit at least a portion of a received RF transmission thatrepresents an inquiry as to the presence of one or more wireless two-wayRF data communication devices if the received RF transmission includesspecific data that corresponds to at least one maintained commondesignation.
 14. The data communications network of claim 13, whereineach wireless two-way RF data communication device enters a second statefrom the first state upon transmitting a response when, (a) theidentified specific data includes data representative of an inquiry asto the presence of one or more wireless two-way RF data communicationdevices, and (b) the identified specific data includes data thatcorresponds to at least one maintained common designation.
 15. The datacommunications network of claim 13, wherein each wireless two-way RFdata communication device enters the first state from a second stateupon receiving, through a sensor interface of the wireless two-way RFdata communication device, one or more sensor signals indicative of apredetermined condition.
 16. The data communications network of claim13, wherein each wireless two-way RF data communication device entersthe first state from a second state upon receiving a RF transmissionincluding an instruction to enter the first state.
 17. The datacommunications network of claim 13, wherein each wireless two-way RFdata communication device enters the first state from a second stateupon expiration of predetermined period of time as indicated by a timerof the wireless two-way RF data communication device.
 18. The datacommunications network of claim 13, wherein each wireless two-way RFdata communication device enters the first state from a second stateafter a predetermined number of failed attempts to communicate by thewireless two-way RF data communication device have occurred.
 19. Thedata communications network of claim 13, wherein each wireless two-wayRF data communication device enters a second state from the first stateupon receiving a RF transmission including an instruction to enter thesecond state.
 20. A method of selectively retransmitting RFtransmissions by a wireless two-way radio frequency (RF) datacommunication device comprising a data packet radio component, themethod comprising: (a) receiving RF transmissions; (b) maintaining atleast one common designation for purposes of filtering RF transmissionsreceived by the wireless two-way RF data communication device; (c)identifying specific data in a received RF transmission and, in responseto the received RF transmission in which the specific data isidentified, (A) transmitting a response, (I) if the identified specificdata includes data representative of an inquiry as to the presence ofone or more wireless two-way RF data communication devices, and (II) ifthe identified specific data includes data that corresponds to at leastone maintained common designation, and (B) retransmitting at least aportion of the received RF transmission as an inquiry as to the presenceof one or more wireless two-way RF data communication devices, (I) ifthe identified specific data includes data representative of an inquiryas to the presence of one or more wireless two-way RF data communicationdevices, and (II) if the identified specific data corresponds to atleast one maintained common designation.